The U.S. Air Force on Sunday said the coalition plane that crashed the day before in southern Afghanistan, killing four service members, was an MC-12 Liberty aircraft.

The twin-engine turboprop plane provides intelligence, surveillance and reconnaissance, or direct support to ground forces. It crashed in Zabul province, about 110 miles (177 kilometers) northeast of Kandahar Air Field, the Air Force statement said.

The four Air Force service members, whose bodies were recovered, were deployed to the 361st Expeditionary Reconnaissance Squadron with the 451st Air Expeditionary Wing at Kandahar Air Field, the statement said. The cause of the accident is under investigation, but NATO has said initial reports indicate there was no enemy activity in the area where the plane went down.

We’ve written before about the MC-12 Liberty. Think of it as a sort of manned drone. The shortage of Predator and Reapers available for overhead ISR lead the Air Force to field a number of modified Beech King Air’s to support the mission in Afghanistan.

The MC-12 seem to focus more on direct support of TF ODIN, the counter IED program, than providing routine overwatch.

No word yet on the cause of the crash. The C-12 family has an excellent safety record.

No sign of enemy action, in spite of what the Taliban may claim. Some reports of a load shift changing the center of gravity. That fits the video, but it is hardly conclusive. Other issues could include a faulty configuration for take-off or crew error. The B747-400F normally has an operating crew of 2, but this aircraft has 7 souls on board. All were lost.

I’m reminded of a picture my dad used to have, very similar to this one. One each of every aircraft type stationed at NAS Whidbey when he was first stationed there in 1973 posed on the ramp. It was a wonderfully eclectic mix, with the then ultra modern A-6E and EA-6B juxtaposed with the SP-2H, C-118 and C-119 and a few other odds and ends that slip my mind. Sadly, when the folks downsized for the move to the desert, that’s one of the pics that didn’t make the cut.

Virgin Galactic’s SpaceShipTwo rocket plane lit its engine for the first time in flight Monday, powering through the speed of sound and moving a step closer to spaceflight for the masses.

The spaceship fired its hybrid rocket engine for about 16 seconds after dropping from the belly of its WhiteKnightTwo carrier plane, long enough to accelerate past the sound barrier and release a stream of exhaust visible from the ground, delighting throngs of spectators near the test site in Mojave, Calif.

Triggered by pilots at the controls of SpaceShipTwo, the rocket firing occurred at about 7:50 a.m. local time (10:50 a.m. EDT; 1450 GMT), about 45 minutes after the mothership and SpaceShipTwo took off from Mojave Air and Space Port.

SpaceShipTwo reached a top speed of Mach 1.2 and a peak altitude of 55,000 feet, according to Virgin Galactic.

There’s nothing particularly wrong with using competing technology demonstrators. The problem came when the program treated a technology demonstrator as a prototype for an actual combat aircraft. Neither JSF demonstrator was fundamentally incapable of being developed. Both teams should have been invited to compete for the actual JSF contract. But necking down at the technology demonstrator phase, intended to spare the expense of developing two fighters, left the government with only one design, in effect, a monopoly. And we’ve seen how well that worked out.

Aerial delivery tests, as part of further operational demonstrations were conducted at China Lake, CA using dummies for static-line drop tests. Cargo drops with 5000lb to 20,000lb were also conducted from an altitude of about 4750ft. The heaviest drop was a 28,243lb load of CDS containers. The primary result of the drop tests found the troop door was too narrow.

The YC-15 also tested mid air refueling as both a tanker and receiver in May-June 1976. 102 hookups were made with a KC-135. Fuel transfer to the receiver was found to be slow (partly because the UARRSI was not designed for the aircraft). Trails of the YC-15 potential tanker aircraft used Navy and Marine Corps aircraft fly a position slightly below and behind the aircraft to simulate the probe-and-drogue method of aerial refueling.

One of the YC-15 aircraft receives fuel from a USAF KC-135.

A YC-15 acts as a tanker with a Navy F-14 Phantom flying in the “tanker-box.”

On 15 to 17 December 1975 YC-15 876 tested ground loading of Army vehicles.

An AH-1 Cobra being loading aboard a YC-15.

A McDonnell Douglas advertisement for the YC-15 showing an M-109 at the rear cargo door.

Overall the YC-15 was found to be a good airplane but had marginal maintainability. 2 of the biggest issues were was engine maintenance and the flight control system. Naturally the YC-15 was going to have maintenance issues because it, like all research aircraft, was intended to test technology and not necessarily representative of an optimized “production-type” aircraft (I remind the reader to a look at the differences between the YF-22 and F-22). Phase 1 tests ended in 18 August 1976. By then both aircraft accumulated 226 flights over 472.8 hours. The YC-15 demonstrated an ability to fly as slow as 62kt to a fast as Mach .78. The initial phases of flight test validates EBF as a valid solution to the STOL problem.

Phase II of the AMST program for the YC-15 began on 7 September 1976. Both aircraft underwent a number of modifications including having a CFM-56 turbofan engine installed on the #4 engine pylon. The wingspan was extended by 22.3ft as a result the wing area went from 367ft2 to 2107ft2! A fighter-type stick was also installed.

Previously shown picture of the YC-15 showing the installed CFM-56 engine on the #4 engine pylon.

On the software side, aircraft 876 had a number of modifications installed including a thrust management system (required because of the increased thrust of the CFM-56) (TMS), an Engine Failure Detection System (EFDS), a digital SCAS and the VAM was improved with a flight director indicator.

Phase 2 testing resumed 12 February 1977 and resulted in 49 sorties for 125.6 flight hours. 876 also went on a tour to NATO member nations in Europe.

In Phase III testing aircraft 875 was returned to original configuration but had a Gross Weight Selector (GWS). The GWS would calculate the optimum flap angle for a given gross weight at various flight conditions. The DLC was improved to operated with and engine out on final approach. All these modifications (including the increased aspect ratio of the wing) resulted in a 10kt reduction in approach speed. The final tally for Phase III testing included 416 flights over 796.3 hours total for both aircraft.

By February 1978 both YC-15s were placed into storage at Edwards AFB.

Part IV will detail the technological contributions the YC-15 made to the C-17 program and the return to flight of the YC-15 in support of that program.

Part one is a general description of the YC-15 aircraft. You can view that here. This post will detail the flight test program of the YC-15.

There were 2 YC-15 aircraft,serials 72-01875 and 72-01876. 875 was rolled on 5 August 1975. The first flight was 26 August 1975. 875 flew from the Douglas plant in Long Beach, CA to Edwards AFB. The only problem during this 2.5 hour flight was a landing gear door found to be ajar. The flight itself was therefore speed limited to 200kts at 20,000ft.

875 flew 3 times over the next 3 days, conducting general flight envelope verification and expansion tests. A further 2 weeks were conducting 7 air-worthiness flights. On 12 September, 875 moved to a Douglas Aircraft Company (DAC) test facility at Yuma, AZ.

876 flew for the first time on 5 December 1975. This flight took the aircraft from Long Beach, CA to join 875 at Yuma AZ.

The YC-15 Joint Test Force (JTF) personnel from the Air Force Flight Test Center (AFFTC), Air Force Test and Evaluation Center (AFTEC), McDonnell Douglas, Boeing (for the YC-14). The (Air Force Logistics Command (AFLC), Tactical Air Command (TAC), Army and the USMC played minor logistical roles in the flight test program. NASA also sent (short take-off and landing (STOL) engineers to analyse data gleaned in the AMST program. The core pilot cadre for the YC-15 was made up of 3 contractors, 3 AFFTC and 3 AFTEC pilots. The competing aircraft were housed in separate hangars with the JTF office between the 2 contactors. This became the model for both the ATF and JSF programs.

The consensus amongst the test pilots and crews was that the YC-15 had generally good handling qualities. The aircraft was easy to fly with the SCAS off and on. There was concern that the pilot could overload the aircraft with the SCAS off but control forces were considered light in both modes.

There was some discussion on whether or not the YC-15 should have a stick or yoke for control input. The intention was to have a “fighter-type” stick installed but there was some skepticism over it’s suitability from higher up the chain-of-command so the stick was removed. To counter, it was argued that the yoke obscured the view of the instrument panel.

The YC-15 had no natural warning upon entering the stall (i.e. vibration) so warning for the stall relied on an artificial “stick-shaker” to provide some warning within the critical angle of attack. This was judged as an inadequate solution because the shaker could activate in conditions of high thrust and flap settings when the aircraft clearly wasn’t in a stalling condition and because a high stink rate (such as during a STOL landing) could mask stalling conditions. As such, a Supplemental Stall Recognition System (SSRS) was developed and tested during the program. The SSRS provided an aural warning when the aircraft approached critical alpha during a given flight condition.

At gross weights of 149,300 the YC-15 flew STOL approaches at 87kts at a 6 degree glideslope giving a sink rate of 15.4 degrees per second. Conventional Takeoff and Landing (CTOL) approaches were normally made a 127 kts with a typical 8-12 feet per second sink rate with no flare at touch down. In STOL mode the aim-point for touch down was about 300 feet from the runway threshold . The YC-15 tested both flare and no-flare landing techniques in STOL mode. Testing at Edwards AFB showed the YC-15 was unable to land consistently in “hot-and-high” conditions in the required 2000 feet because of the slow actuation of the thrust reversers.

The thrust reversers could be used in-flight with some minor airframe buffet.

Testing the VAM, used approaches very similar to Navy carrier approaches were airspeed on approach is governed by angle of attack. The major issue was that the VAM didn’t display enough information to enable a completely “eyes-out-of-cockpit” approach.

33 STOL and CTOL off field demo landings, at Edwards, were conducted on 5000ft x 200ft runways with markers placed at 2000ft x 60ft. 5 pilots flew these tests and the YC-15s landing gear tire pressure was reduced. It was also found that the YC-15 could taxi over a 4-inch dump at 75-80kts. A unique procedures for the YC-15 during a STOL takeoff was extending the flaps from 14 to 23 degrees during the takeoff roll. Below is some archive video of STOL testing in 1975 (please pardon the music, Creed’s “Higher” just doesn’t work IMO):

[youtube https://www.youtube.com/watch?v=VUcxRhl3Txo]

During testing cracks were found in the blown flap material and fasteners had to replaced on a cracked rob. This was due to repeated exposure of hot jet exhaust. Direct Lift Control (DLC) (*see update below) was found to be effective for corrected high approach errors in the glide-slope but wasn’t effective for getting too low during approach. Flight path correction was done with a slightly high arrival at glideslope,correct with DLC, and then add thrust. Maximum DLC deflection angle was 20 degrees from flush on the upper surface of the wing. Orientation of the DLC actuation in the cockpit was a major “human factors” issue of debate among the pilots.

The YC-15 displayed docile engine out characteristics with mild crew indication 4-6 seconds after an engine out occurred. The YC-15 also was unable to meet the range requirement of 2600nm. The aircraft had more drag than predicted giving it a range of 1760nm.

I’ll be standing fast on this post for now. I’m splitting part 2 into this and an additional part detailing some of the operational and international demonstrations as well as technical improvements and further flight test results.

*[UPDATE]: For reader that may not know, direct lift control (DLC) is a system of spoilers, located on the upper surface of the wing. that either differencially control roll and in unison control pitch by dumping lift from the wings. They are common to most airliners.

Navy Lieutenant Alan Wood, Communications Officer aboard LST 779, the man who provided the second and larger Iwo Jima flag raised by the patrol of 28th Marines in the war’s most iconic image, has passed away at 90.

Semper Fidelis, Lieutenant Wood. You may report into the growing formation of heroes mustering on the fantail above.